I have problem with consistency paranoia in DDD. I still want to validate relation between objects and sometimes it feels like I’m over-validating stuff. For example:

Aggregate1: Payment(id, merchantId, posId)
Aggregate2: Merchant(id)
Aggregate3: Store(id, merchantId)
Aggregate4: Pos(id, storeId, merchantId)

Payment payment = merchant.createPayment(pos, store); // here i did validations 

later, second transaction:

payment.prepareRequest(pos, merchant, store); 

Is it ok to firstly check if payment.wasCreatedBy(pos) and if pos.belongsTo(store) and if store.belongsTo(merchant) and then, when everything is fine do actual request preparation with lets say:

PosInfo posInfo = pos.info(); StoreInfo storeInfo = store.info(); MerchantInfo merchantInfo = merchant.info();  return new PreparedRequest(posInfo, storeInfo, merchantInfo); 

Or should I just do this in app service:

PosInfo info = posRepository.find(posId).info(); StoreInfo info = storeRepository.find(storeId).info(); MerchantInfo info = merchantRepository.find(merchantId).info(); Payment payment = paymentRepository.find(paymentId); PreparedRequest req = payment.prepareRequest(posInfo, merchantInfo, storeInfo); 

without any validation? Should I expect that application service will prepare data correctly or should I prevent creating such “request” when some relation is invalid – be paranoid?